[mep]

Hello all,

I'm currently trying to run an analysis using temperature integrated simpleFoam. As of my observations, temperature range for the fluid is between 20-50 C and due to this large range, viscosity changes in a wide range which leads my computation into a big error, at about 50%.

So here is my question. I would like to apply a curve-fitting to viscosity of my fluid flowing through and integrate it in the OpenFOAM by NOT using a non-Newtonian approach. Because fluid is definetely Newtonian.

How can I achieve it?

[Tobi]

There are more options. Either you switch to, e.g., rhoSimpleFoam and use a polynomial approach or you derive your current solver (simpleFoam) and implement new volScalarField´s which relates to temperature and viscosity. Then you have to solve an appropriate temperature/energy equation and calculate the viscosity based on your temperature field.

Probably, the rhoSimpleFoam solver fits better as you don´t have to program anything yourself. An example:

thermoType
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       polynomial;
    thermo          hPolynomialt;
    equationOfState polynomial;
    specie          specie;
    energy          sensibleEnthalpy;
}

The thermo and equation of state polynomials might be just set-up with the first coefficient (its the constant). The transport polynomial is related to the viscosity.

[mep]

Thank you for your reply Tobi,


The thing is I would like to compute the viscosity for each cell using its temperature and have this value used in governing equations. I don't want any contour for viscosity, to say. Do you have any recommendation for this goal?

Originally Posted by Tobi

There are more options. Either you switch to, e.g., rhoSimpleFoam and use a polynomial approach or you derive your current solver (simpleFoam) and implement new volScalarField´s which relates to temperature and viscosity. Then you have to solve an appropriate temperature/energy equation and calculate the viscosity based on your temperature field.

Probably, the rhoSimpleFoam solver fits better as you don´t have to program anything yourself. An example:

thermoType
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       polynomial;
    thermo          hPolynomialt;
    equationOfState polynomial;
    specie          specie;
    energy          sensibleEnthalpy;
}

The thermo and equation of state polynomials might be just set-up with the first coefficient (its the constant). The transport polynomial is related to the viscosity.

[Tobi]

Well, I am not sure if you read my reply or not because I wrote the stuff you need. Hence, I don't get your statement.

[mep]

Thank you for your help and kindness.

[Tobi]

Just a quick question. Is it clear to you now or not? I don't have the feeling that my statement is sufficient for you or maybe I misunderstood your inquiry!?